factor of 10

[sayeed of the road]

If I got this right 10 is the max ratio of available charge current to battery capacity

is the "why" explained somewhere?

[Alanb]

C/10 is generally quoted as maximum charging current on battery manufacturers data sheets for Flooded Lead Acid (FLA) batteries.

 

I would hope that the manufurers, are those best qualified to give advice on maintaining their batteries.

 

It is to be expected that exceeding the C/10 charging rate on a regular basis, would shorten battery life.

 

Alan

[Derek Uzzell]

This link should provide sufficient explanation.

 

https://www.ecosoch.com/solar-battery/

[colin]

Another source of info.

http://www.aandncaravanservices.co.uk/battery-charging-faults.php

[sayeed of the road]

Thanks for the links

 

Not sure either of them answer my query which is about the factor of 10 (not the C rate)

It was mentioned by a retailer who said that as my charger had a max charging current of 18A then (using the factor of 10) the max battery bank should be no more than 180Ah (I have 200Ah fitted)

 

C rate is pretty well documented but googles on "factor of 10" throw up a lot of info about mobile phones and suncream

 

As I'm about to buy 2 new LABs I thought I ought to understand any limitations / disadvantages / danger of buying batts that might be too big for the charger.

How important is the "factor of 10"

 

[Ocsid]

The one tenth Amp figure of the Ah is not set in concrete nor necessarily something you have to achieve, its actually more a figure if you exceed it "could" be life limiting. Under rating it within reasonable levels is no bad thing, more beneficial if that under rating is not taken to extremes, so I am very surprised a dealer states your 18 Amp charge is unsuitable for a 200AH bank.

 

Some deep cycling batteries can't even cope with as high as one tenth.

 

As an aside here, in our application taking the opportunity to grab a fast charge is often considered beneficial, get well charged up whilst you travel, so exceeding one tenth can be "worthwhile", even if it comes with some abuse. Go for more moderate charging rates and get a longer battery life, is another option. All part of the balance of compromises we make in battery choice etc to best suit our needs.

[Derek Uzzell]

Sayeed

 

In this link

 

http://www.chargingchargers.com/tutorials/charging.html

 

the following statement is made.

 

Most battery manufacturers recommend sizing the charger at about 25% of the battery capacity (ah = amp hour capacity). Thus, a 100 ah battery would take about a 25 amp charger (or less). Larger chargers may be used to decrease charge time, but may decrease battery life. Smaller chargers are fine for long term floating, e.g. a 1 or 2 amp "smart charger" can be used for battery maintenance between higher amp cycle use. Some batteries specify 10% of capacity (.1 X C) as the charge rate, and while this doesn't hurt anything, a good microprocessor charger of the appropriate charge profile should be fine up to the 25% rate. You talk to different engineers, even at the same company, you get different answers.

 

CTEK advertises their MXS 10 10A battery charger as follows:

 

The MXS 10 is a fully automatic 8-step charger that delivers 10A to 12V batteries from 20-200Ah and is also suitable for maintenance charging up to 300Ah. It includes battery diagnosis to establish whether your battery can receive and retain a charge, a Recond mode for restoring and reconditioning stratified and deeply discharged batteries, a winter program for charging in cold weather and an AGM option which maximises the performance life of most Stop/Start batteries. The MXS 10 also has a temperature sensor for optimised charging and it can even be used as a power supply source for 12V equipment.

 

My 2015 Rapido motorhome has a CBE-made 16A onboard battery charger and the standard specification included a 100Ah Banner leisure battery. There was a long-standing Rapido factory-option to add a 2nd 100Ah Banner leisure battery, but the battery charger always remained the same 16A model.

 

This is ‘rule of thumb’ territory and comes down to real-world usage. Although it might be argued that a charger with an output above 18A should be beneficial when the total capacity of the leisure batteries exceeds 180Ah, as you’ve been operating your motorhome (presumably without any battery-related problems) for years with a 18A charger/200Ah battery combination, it’s reasonable to assume that your 18A charger can satisfactorily cope with 200Ah of batteries. (Obviously, if you were planning to replace your current 200Ah of leisure battery capacity with (say) 2 x 180Ah batteries, your present charger might well prove inadequate.)