HELP !! Technical stuff about batteries and charging Forums

rithym

Firstly Hi to all and apologies if this is a bit of a dense question.

Our Burstner 747 has two 75Ah leisure batteries aswell as the engine starter battery. If my understanding is correct the present setup goes along these lines...

When the engine is running the starter and leisure batteries are split charged from the alternator until they reach a certain voltage then
they individually receive a float charge to keep them topped up. Alternatively when we are plugged into mains the leisure batteries get the lions share of the charge and the starter battery gets a float voltage [rough quote from the handbook]

Problem is the 150Ah leisure batteries are not enough to run all the gadgets, laptop, TV, etc when we are away from electric hookup more than one day/ night. With this in mind we have bought two more 110Ah leisure batteries which we would like to keep seperate from the existing system to run the 400W inverter which powers TV, stereo, etc.

The bit where it gets complicated for us is the best way to charge this new 220Ah system when we are driving AND when we are hooked up AND on the odd occasion when we run the generator for the washing machine.

Sterling power [url]http://www.sterling-power.com/htm/btb.htm[/url] have a dc-dc 4 stage charger advertised on their website which we thought if connected in at the right place would cover our charging needs for all the above scenarios and negate the need for a standard 230v charger.

Question is do we wire it in to the starter battery (which only gets a float voltage when mains is on) or do we wire it into the existing leisure batteries which get charged when the engine is running and when plugged into mains?

Has anyone else added a similar setup and if so how do you charge the extra battery bank?

TIA

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DABurleigh

Before you spend a lot of money (and the battery-to-battery charger IS a valid solution to the specific question you asked), I would be sorely tempted to substitute, if only temporarily, your new 220Ah for the old 150Ah and see how you get on. The numbers aren't that hugely different, I know, but I suspect the significance may be in old versus new!

An awful lot of energy is supposedly being consumed in 24hrs otherwise, which makes me suspect it isn't there useable in the old batteries to start with.

Dave

jabber

You will get a lot more charge in your batteries if you use a stepped charger when on mains, this could make a big difference. It may be that your MH has one, but unlikely.

Sterling and Waeco make good chargers of this type and they can charge your motor battery as well.

An alternative could be to use the CTek 3600 before you set out and when on site overnight, this should give a good full charge as well.

Battery to Battery has good reports, but I don't know how it may affect your alternator with the greater load!

John Cool

rithym

Thanks to John & Dave for the swift replies.

Just to further clarify our situation we recently had the two standard 150Ah leisure batteries checked at a local battery specialist the man said all the cells are good he put a hydrometer in and read the acid density or something. So we came to the conclusion that we were probably using more current than they were reasonably capable of supplying, hence the purchase of two more.

The present charger on the van is a Realtek it has iUoU on the front which we believe means 4 step charging. Can't read the rating which we assume is on the back without removing the unit which looks like a major task (wires and plugs everywhere) If this charger is clever enough to charge the orignal leisure batteries both whilst driving and when hooked up then we thought by linking in a dc-dc charger at that point it would also charge the new 220Ah aswell. Another consideration is to parallel all four batteries together but this did not seem wise as they are different ampage's. Also mixing new and old is, we are told, a no no.

We understand the best solution is to buy a good 3 or 4 stage mains charger and plug in whenever possible but that takes no account for when the engine is driving the 120A alternator. Of course we could run the generator more often? As the dc-dc charger is probably the same price as a good mains charger we thought that arrangement may make better use of mains and alternator?

Giok

While your battery acid analysis may be OK it doesn't test all aspects of your battery, and a good electrical place like LSUK have a clever little meter which tells you all the properties of a battery's health, like cold cranking power etc. I agree that it sounds as though your original batteries are getting tired, as suggested swap them with your new 150 Ah batts and see what happens. If you do have to get another two new batteries at least you'll be able to match them all up. I always reckon 2 years is the maximum efficient life of any battery.
John