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multi battery set up


kellyv8
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I'm running 3 batteries in my Disco. Two under the bonnet and a 95amp/hr sealed unit in the back.

The two auxillaries are hooked up together and receive charge via a solonoid that swaps between them and the starting battery depending on the voltage. No need for a second alternator. The solonoid cost $150 and I've also got it protected with circuit breakers. Another good idea is to fit a button to transfer power from your auxillaries to the starter battery to start the car if the main battery happens to go flat.

This setup has worked fine for over a year now running a fridge, lights & stereo. Some people like to spend $1000+ on a battery management system but I personally don't see the need. I can post some photos if you like.

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150 aus$ ?! I don't know what the Aus exchange rate is like, but you can buy these for not much money at all, especially if you can make up your own leads.

X-Charge%201.jpg

when charging, the batteries will all be in parllel, this is typically the same, whether you use a £5 manual switch or a £500 rip off of a solenoid. you have to spend a lot more to get independent current and voltage controlled charging.

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you can fit as many relays as you wish to split them up however you wish.

But rather than get that many bats, why not just get two decent ones ?

G

its my own personal preference on how many batterys i run really

and at the minute i have one optima for each winch and one for starting

i currently use the x charge which is very good i must say

but at the mo it only isolates the starter battery from the winch batterys which are connected

ideally i would like eacch battery to be seperate so can i use mutiple splt chargers

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the relay is just a beefed up spot light relay really you can run lots of them but inevitably when the car is on there all being charged the same its only when its off that they all go separate

how are you trying to set them up so if one goes flat it doesnt draw the rest down?

if your suffering from charge loss change the optimas i had now but trouble from them

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and at the minute i have one optima for each winch and one for starting

Except you don't, not really.

When you're winching normally, the engine should be on and all relays closed, so you are drawing from all three. the winch can't 'choose' which to draw from.

If you were to suffer engine failure,water ingress etc and wish to recover yourself on batteries alone, i think you would be better off to draw from two batteries, whichever winch you're using, and keep the engine battery healthy for starting once you're ready to start the engine again.

The benefit of isolating all the batteries from each other is that you will prevent them trickle charging in to each other and shortening their livespan.

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Except you don't, not really.

When you're winching normally, the engine should be on and all relays closed, so you are drawing from all three. the winch can't 'choose' which to draw from.

If you were to suffer engine failure,water ingress etc and wish to recover yourself on batteries alone, i think you would be better off to draw from two batteries, whichever winch you're using, and keep the engine battery healthy for starting once you're ready to start the engine again.

The benefit of isolating all the batteries from each other is that you will prevent them trickle charging in to each other and shortening their livespan.

i am aware of this trickling effect thats why i want to isolate them, so a battery per winch

the split charge is doing exactly what you say keeping the starter battry fully charged this i want to keep aswell as isolating one battery per winch so i dont get the trickle effect

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This split charge diode will manage 3 batteries, keeps them completely isolated. The 3 output version is about £80.

All down to how much you wish to spend...

this looks like just the thing cheers

now to be a right awkward bugger can i run this system with the x charge unit ie this sterling system isolating the winch batterys completly and then the x charge to keep the starter battery seperate

sorry to be a pain but my knowledge of electris are nil

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Buy another X-charge simple, the diode based ones have some flaws. Apparently (and I do not pretend to understand this), when one passes a voltage through a diode, you loose some voltage. This reduction in voltage means that the batteries beyond the diode never see the whole output from the alternator and thus will not fully charge. Or something. A grown-up will be along shortly...

Chris

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Buy another X-charge simple, the diode based ones have some flaws. Apparently (and I do not pretend to understand this), when one passes a voltage through a diode, you loose some voltage. This reduction in voltage means that the batteries beyond the diode never see the whole output from the alternator and thus will not fully charge. Or something. A grown-up will be along shortly...

Chris

Have a read of Sterling Power's facts and figures page about the diode system, it's quite well explained. Yes there is a SMALL voltage loss, but it's not that significant.

If you use a split charge diode, it's a very simple setup. One alternator feeding it, and multiple batteries charging from it. Each battery is totally isolated from the others, so there's no need for any further relays. The only other thing you may choose to add is a safety isolator switch between the battery and the device running from it (winch, fridge or other).

I have no connection with this company, just happened upon their products myself a year or so back when I was researching dual battery setups.

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Diodes are a perfectly reasonable way to achieve split charging. Both relay and diode systems have pro's and con's - and it's just a case of weighing up which are more important to each application.

Diode

Pro:

* Complete isolation (your main battery can never be discharged while winching)

* No cross flow current means diodes only need to be rated up to the Alternator peak current.

Con:

* Cannot be used with battery sensed Alternators (300tdi, Td5, Puma and probably the BMW period engines)

* 0.7v drop - which leads to effectively loosing 6% of your alternators output current.

* Can be damaged by voltage spikes such as are caused by welding

Relay

Pro:

* Universal - can be used on any type of charging system.

* Complete isolation while vehicle is not running (your fridge or lights will not compromise starting ability).

* Increased current delivery and capacity when vehicle running by utilising both batteries.

* Can be wired to give a 'push button' jump start

Con:

* Main battery can be discharged while vehicle is running (although connection losses reduce the draw on the main battery versus the Aux Battery)

* Can be damaged by high cross-flow currents

Just for completeness,

Managed / MOSFET Split Charge

Pro:

* No (very small 0.05v) voltage drop

* Managed charge cycles can extend the life of batteries.

* Usually have battery voltage / condition indicators, sometimes remote, in cab.

* Can be programmed for complete isolation, no isolation or a mix.

* lots of blue flashing LED's

Con:

* Normally contain a computer (microcontroller) (Personally, I don't mind this - but it's not to everybody's taste)

* Sensitive to voltage spikes - things like dodgy starter or winch motors as well as welding.

* Susceptible to water ingress (in some cases)

* Not as mechanically robust as Diodes or Relays

* Expensive

As you can see there is not a lot in it between the different types. None of the three is universally 'the best' it just depends on your operating environment and requirements.

Si

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its my own personal preference on how many batterys i run really

and at the minute i have one optima for each winch and one for starting

i currently use the x charge which is very good i must say

but at the mo it only isolates the starter battery from the winch batterys which are connected

ideally i would like eacch battery to be seperate so can i use mutiple splt chargers

fair enough. i was assuming you were trying to use lots of cheapo batteries instead of a couple good ones.

now to through a spanner in the works, why do you want a split charge system ? if all your batteries are of the same age, type and condition they can be left connected together.

i've run many multiple battery setups like this (20+ batteries), and see many many more - but always one type of battery is used per install whether they be optima, nsb, hawker etc.

if you still wish to isolate them, just get another x charge system.

G

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