cask Posted March 26, 2009 Share Posted March 26, 2009 Hi everyone, I have a motorhome which has the normal charger for the leisure battery when on hook-up. There is a Battery Master unit fitted which allows the cab battery to be charged using the same charger. This works well. However, the instructions for the Battery Master states:- “If the leisure battery is not being charged in any way then Battery Master will allow the engine and leisure batteries to share the discharge load thus greatly increasing the time before the vehicle will fail to start.” I have checked this by leaving the radio and interior lights on,and both batteries had their voltage reduced by the same amount. I stopped the test when the voltage was 12.20.[ The radio is also fed from the leisure battery.] I would rather have the cab battery left separate so that I can start the engine when required. My question is - apart from introducing a switch to isolate the Battery Master when not on mains hook-up, can a simple automatic switching system be fitted to achieve the same end result? [sorry this is rather a long posting,] Andrew Link to comment Share on other sites More sharing options...
Brambles Posted March 26, 2009 Share Posted March 26, 2009 Hi Andrew. One posiibility is to fit a mains powered relay to close the circuit to the vehicle battery when on hook up. So no mains hook up, vehicle battery will not be discharged as relay switching contacts wil be open. I am not familiar with the Battery master system to know if there is a better option, or indeed one built into the system to select how it works. I lawys though the Battery Master was purely for charging the vehicle battery from the lisure battery should it becomne discharged... I seem to be wrong from what you have said and it allows both batteries to supply power for liesure use. Jon. Link to comment Share on other sites More sharing options...
davenewellhome Posted March 27, 2009 Share Posted March 27, 2009 The battery master will trickle a small charge from the leisure battery to the engine battery when the leisure battery is in a higher state of charge than the engine battery. It will not pass charge the other way. The idea is to extend the period of time it takes for the engine battery to be depleted to the point where it won't start the engine. If you isolate the BM you will in effect be shooting yourself in the foot as it will have exactly the opposite effect that you want. D. Link to comment Share on other sites More sharing options...
Brambles Posted March 27, 2009 Share Posted March 27, 2009 Hi Dave, Thanks for the explanation, so in efect the following posted by Cask taken from instructions, is misleading or a least confusing. “If the leisure battery is not being charged in any way then Battery Master will allow the engine and leisure batteries to share the discharge load thus greatly increasing the time before the vehicle will fail to start.” What I don't understand is when he tested it the vehicle battery discharged also. This contracticts the idea that charge cannot pass the other way which I accept is the way I thought it worked also. Jon. Link to comment Share on other sites More sharing options...
Brambles Posted March 27, 2009 Share Posted March 27, 2009 I have now looked at info on Battery Master which confirms what you have said Dave - Emphatic, NO, charge cannot go from engine battery to Leisure battery. I did not doubt what you were saying ...well maybe a little if I am honest. So this begs the question, is Cask's battery master wired correctly when his test showed the engine battery drop with the leisure battery? Link to comment Share on other sites More sharing options...
Keithl Posted March 27, 2009 Share Posted March 27, 2009 But what Cask did not say is which battery the interior light he left on was running from. He said the radio was wired to the leisure battery but made no mention of the interior light. If the light was running from the vehicle battery then his test was conclusive, if from his leisure battery then inconclusive. If he re-ran the test with only the radio on then only the leisure battery should discharge. Keith. Link to comment Share on other sites More sharing options...
Brambles Posted March 27, 2009 Share Posted March 27, 2009 Hi, He said radio was also connected leisure battery. Also to me means lights also from leisure battery. However even if the vehicle it is still inconclusive as radio could have brought leisure down more than lights and battery master fed power from vehicle to leisure as wired wrong. e.g battery connections swapped over. ...I hope this is helping you Cask - us talking amongst ourselves.. Jon. Link to comment Share on other sites More sharing options...
cask Posted March 27, 2009 Author Share Posted March 27, 2009 Thanks for all of the comments and suggestions, I agree the web site for the Battery Master does say there is not a drain from the cab battery to the leisure battery on one page but in the User Instructions it says "If the leisure battery is being charged by mains hook-up or solar panels, Battery Master will maintain the engine battery indefinitely even if it is being discharged by an alarm, radio, clock etc. If the leisure battery is not being charged in any way then Battery Master will allow the engine and leisure batteries to share the discharge load thus greatly increasing the time before the vehicle will fail to start." Having tested the radio and interior lights [both are from the leisure battery] I can confirm both batteries are linked and discharge together when no mains hook-up is present. I have talked to the suppliers and they agree that when not on hook-up the batteries are linked and the Battery Master only "shuts down" when the voltage reaches 11.40 volts! The idea of a switch was to have a circuit when on hook-up but when not, to break the circuit that links the two batteries. The idea of a mains relay seems ideal but the charger can take 17 amps so a suitable relay able to take this gets rather large and expensive. The unit is fitted correctly [by the suppliers] as it works on mains hook-up perfectly. Battery_Master_Customer_instructions.pdf Link to comment Share on other sites More sharing options...
davenewellhome Posted March 27, 2009 Share Posted March 27, 2009 The discharge load that BM will allow the two batteries to share is that which is connected to the engine battery, under normal circumstances this will be caused by alarm, radio, engine management ECU. As Cask's radio is connected to the leisure battery that is the battery that will suffer the load of the radio and not the engine battery. The engine battery will suffer the load of the alarm and engine management ECU etc. I would suggest that the fact that both batteries discharged at the same rate is more coincidence than planning with the radio being connected to the leisure battery. D. Link to comment Share on other sites More sharing options...
Brambles Posted March 27, 2009 Share Posted March 27, 2009 "I have talked to the suppliers and they agree that when not on hook-up the batteries are linked and the Battery Master only "shuts down" when the voltage reaches 11.40 volts! " The above is the key here. Seems the suppliers contradict what is believed from the BatteryMaster Website details and what Dave is saying and he is very experienced with these things. So does the Vehicle battery drain at same time as the Leisure Battery or not? It appears so from Cask's tests, and what the suppliers say. Down to a set voltage. Cask, the relay need not be expensive. 17 Amps is not a lot and there are many relalys capable of 30 amps at 12 volts switching. One simple way is to use a mains to 12 volt transformer type trickle charger. This could be used to energise a standard automotive 30 Amp relay readily available. Saves you having to wire up mains and mount a mains energised relay. An example of a mains relay is shown here http://www.maplin.co.uk/Module.aspx?ModuleNo=37495 3rd item is 240 volts, and 1st is a base for the relay. This is just as an example and is not expensive. Jon Link to comment Share on other sites More sharing options...
tp002c784tp002c784tp Posted March 27, 2009 Share Posted March 27, 2009 cask - 2009-03-26 7:30 PM Hi everyone, I have a motorhome which has the normal charger for the leisure battery when on hook-up. There is a Battery Master unit fitted which allows the cab battery to be charged using the same charger. This works well. However, the instructions for the Battery Master states:- “If the leisure battery is not being charged in any way then Battery Master will allow the engine and leisure batteries to share the discharge load thus greatly increasing the time before the vehicle will fail to start.” I have checked this by leaving the radio and interior lights on,and both batteries had their voltage reduced by the same amount. I stopped the test when the voltage was 12.20.[ The radio is also fed from the leisure battery.] I would rather have the cab battery left separate so that I can start the engine when required. My question is - apart from introducing a switch to isolate the Battery Master when not on mains hook-up, can a simple automatic switching system be fitted to achieve the same end result? [sorry this is rather a long posting,] Andrew Hi Cask I know this is not much help in your case, but I have a Battery Master fitted on my Lunar Roadstar and I also have a 80w solar panel, This arangement is brilliant, My vehicle has not been run for six weeks and I tested the system today and both the Leisure and Main battery's read 14.2 volts. Last year when I had my habitation test done when they tested the electrics I don't know how they managed it they blew two fuses in my split charge relays and the way I found out was when I tested the state of the battery's a couple of weeks later the leisure batterys stood at 14volts but the main battery only read 12.6, this proved how well the Battery Master worked. Terry Link to comment Share on other sites More sharing options...
davenewellhome Posted March 27, 2009 Share Posted March 27, 2009 I have to say that looking back over the posts from Cask that the BM may have been connected back to front, in effect passing charge from engine to leisure battery instead of leisure to engine. difficult to be certain without actually having the vehicle in front of me though. D. Link to comment Share on other sites More sharing options...
Brambles Posted March 27, 2009 Share Posted March 27, 2009 I am inclined to agree. The way to test this would be to draw power from the main battery - put the side lights on (button below key and turn anticlockwise) and let it pull the engine battery down a bit and see if the leisure battery is pulled down also. watcha reckon Mr Newell? Link to comment Share on other sites More sharing options...
cask Posted March 27, 2009 Author Share Posted March 27, 2009 Hi Dave, I will double check the connections tomorrow.They are made directly to the rear of the habitation fuse box. I have done various tests over the last two weeks and some give "interesting" results.[All with the hook-up disconnected.] With the radio and internal spot lights on, disconnecting the leisure battery had no effect; they still stayed on. Then disconnecting the cab battery; they not surprisingly went off. Reconnecting the leisure battery and turning on the control panel allowed the lights to come on. The radio was able to be restarted. This I take to mean the two batteries are linked as either can be used as the power supply. When the hook-up is live the voltages of the two batteries are slightly different by 0.02v constant over a 3 hour period [ up to 14.32v the steady] as the batteries are recharging from 12.4v after testing. This I assume means the Battery Master is working correctly as there has to be a small difference in voltage from the leisure battery before the unit will charge the cab battery. Hi Brambles, The suppliers were Van Bitz and the web site for battery Master [inc the pdf I posted ] do indeed contradict themselves, which is why I spoke directly to them. The testing done so far, using 4 hours lights and radio daily for 4 days, to simulalate a normal usage for us, keeps both btteries discharging at exactly the same rate [ measured hourly]. I will try your suggestion about the sidelights tomorrow and report back. Many thanks for your replies, Andrew Link to comment Share on other sites More sharing options...
davenewellhome Posted March 28, 2009 Share Posted March 28, 2009 There would seem to be something peculiar going on with your motorhome "With the radio and internal spot lights on, disconnecting the leisure battery had no effect; they still stayed on. " this would suggest that the radio and internal lights (are these in the cab or living area?) are being powered from the engine battery. The BM will only pass a small current, not enough to run a radio and spot lights usually so it seems unlikely that the BM is passing the power for the lights and radio. I'd have a word with Eddie at Van Bitz as they fitted the unit, while its unlikely that they've fitted it wrongly even I have been known to make the occasional mistake :D and as you're in Devon it shouldn't be too far for you to travel to get it sorted. The BM unit has a two colour LED on it, if both batteries are charged then it should show green but if the engine battery is lower and drawing charge through the BM then it turns red, what colour is the LED showing on yours when you disconnect the leisure battery? D. Link to comment Share on other sites More sharing options...
Brian Kirby Posted March 28, 2009 Share Posted March 28, 2009 In the hope it may be helpful - but this really is amateur night - it sounds to me as though there may be a secondary link between the two batteries, that is fooling the Battery Master. Could this link be via a failed split charging relay, that fails to disconnect when the engine is switched off? Link to comment Share on other sites More sharing options...
Brambles Posted March 28, 2009 Share Posted March 28, 2009 Hi Brain, I doubt it as if the relay failed shorted, then when the engine is started the wiring (and relay) would fry. Or a fuse blow! Jon Link to comment Share on other sites More sharing options...
Brambles Posted March 28, 2009 Share Posted March 28, 2009 Andrew. Brain's comment has got me thinking. Have you got a switch on your Leisure control panel to select the engine battery as a source of power. If so, is the switch set for Leisure only. Jon. Link to comment Share on other sites More sharing options...
cask Posted March 28, 2009 Author Share Posted March 28, 2009 Jon, I tried your suggestion of putting on the side lights them not being on hook-up, checking the voltage drop; over a period of one hour the cab battery dropped from 12.57v to 12.49v, the leisure battery from 12.63v to 12.54v. so I would assume there is a linkage. [i have checked and the selector switch is set to leisure battery.] Dave, I checked the connections for the BM and they are correct. I have tried the radio and internal lights again and found that the radio is fed from the cab battery afterall. The internal lights[four led spots each 200ma consumption] stayed on after the leisure battery was disconnected, but if the BM was also disconnected the lights went off. [Reconnecting the leisure battery allowed the lights to be restarted.] The BM fitting instructions say that the batteries are linked when not on hook-up and this test would appear to confirm this and rule out a secondary feed from the cab battery. Update; I have just tried to see what colour light the BM is showing when the leisure battery is disconnected. I had to reconnect the BM first and then disconnected the leisure battery; this time the interior lights went out! Reconnecting the LB has the BM showing a red light [cab 12.49v, Leisure 12.54v] which I think is correct, with the lights available again. I hope this makes sense to someone... Andrew Link to comment Share on other sites More sharing options...
davenewellhome Posted March 28, 2009 Share Posted March 28, 2009 Hi Andrew, did Van bitz just supply the BM and you (or someone else) fitted it or did they supply and fit? The wiring of the BM is simple with just three wires: brown, red and black. Brown goes to engine battery, black goes to earth and red goes to leisure battery. D. Link to comment Share on other sites More sharing options...
cask Posted March 28, 2009 Author Share Posted March 28, 2009 Hi Dave, Yes, Van bitz fitted the BM. The connections are as you mention. Andrew Link to comment Share on other sites More sharing options...
davenewellhome Posted March 28, 2009 Share Posted March 28, 2009 Hi Andrew, so have you contacted Eddie yet and asked him? D. Link to comment Share on other sites More sharing options...
cask Posted March 28, 2009 Author Share Posted March 28, 2009 Dave, I spoke to Eddie earlier in the week and he was rather puzzled about the readings I was getting. I think he mentioned a current flow of about 1.1 amp max befor the BM shut off. I wonder if the low draw of the led lights was insufficient to cause the BM to break the circuit. If the radio had been taking power from the leisure battery then it would probably shut down due to the "excessive" current flow. Andrew Link to comment Share on other sites More sharing options...
Brian Kirby Posted March 29, 2009 Share Posted March 29, 2009 AndrewCan you take the BM completely out of circuit, and see what happens then? This would (should) reveal if there is any other linkage. Assuming there is not, I wonder if you may have a duff BM? Link to comment Share on other sites More sharing options...
cask Posted March 29, 2009 Author Share Posted March 29, 2009 Brian, I have taken the BM out of the system and there is then no apparent linkage between the two batteries. Disconnecting the LB makes the lights go off at this stage. The batteries were still at the same voltage but reconnecting the BM and testing showed the disconnection of the LB made the lights go out. I am beginning to think along the same lines as you as when the mains hook up allowed the batteries to be charged overnight, testing the system by disconnecting the LB made no difference to the lights; they stayed on! I will be contacting Van Bitz again as I am "confused" [even more so than normal if that it is possible......] Best wishes, Andrew Link to comment Share on other sites More sharing options...
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