Isuzu Trooper Owners Club UK™

[Astroman]

Hi,

I have a 1993 Lotus Bighorn 3.1TD Auto. It has one battery fitted. Even though I have had no problems with starting I have noticed that the engine turns over very slowly when cold (around freezing point) and I wonder what will happen if we get a really cold spell? I note from the handbook that there is a "cold weather option" which has a second battery as part of the kit. Has anyone fitted a second battery? and if so what size and was it simply wired in parallel? how did you secure it? There is an obvious space fror the second battery under the front O/S wing but, other than having a special tray made I can't figure how it would fit.

Thanks,

Chris

[Google]

[Philp]

You'd need a split charge kit, which you can get from good 4x4 specialists and even caravan suppliers to distribute the power, some cables and a second battery tray of some sort.
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Phil

96 or is it a 98 Isuzu Bighorn Lotus

[denis]

Mine came with two batteries, one each side of the engine. How it is wired I have not checked.

I am not sure why philp thinks you need a split charge, because if they are wired in parallel then they should charge at same. However I would check if alternator needs upgrading to provide sufficent power.

Maybe your slow turnover is due to wrong engine oil - there are suggestions in other threads that starting problems can be caused by wrong oil.

[Astroman]

Thanks Philp & Denis,

Yes Denis, I don't think i need a split charge relay as effectively what I'm trying to do is double? the capacity of the "service" battery not have a seperate battery for accessory use as in a caravan. My wife has a Mitsubishi Delica 2.8 TD with twin batteries and they are wired in parallel with heavy duty, approx 10mm dia, cable.(As an aside, you just have to look at the ignition key and it starts - superb!)
I'll check with Isuzu as to whether the alternator needs to be uprated, if it does it's probably cheaper, and easier, to fit a Kenlowe pre-heater. As for oil I'm using a 5/40 semi-synthetic.

Chris

[Peterjday]

Operating batteries hard-wired in parallel can be decidedly dodgy.

The reason is thus: No two batteries are exactly the same, or age in the same way. When they are under charge (connected in parallel) each takes a different amount of current, due to variations in internal resistance, and this translates into different amounts of stored energy and slightly different off-load terminal voltages.

When the engine isn't running and so the alternator isan't supplying current, the battery with the higher terminal voltage will push current through the other. The pont about lead-acid batteries is that they have very low internal impedance (otherwise they wouldn't be able to supply the high currents necessary to start your car) and so quite large currents can circulate around the parallel batteries. Large circulating currents = risk of over-heating and general knackering of said batteries.

Moral - it isn't usually done that way, and if your Delica has them hard-wired in parallel I would put serious money on there being warnings in BIG RED LETTERS in the manual to the effect that they should both be replaced at the same time with identical batteries from the same manufacturer.

A split charge system keeps the batteries mutually isolated and prevents problems.

The people who want high reiability are the military. They get the extra battery power by using two batteries - but wiring them in series to give a 24 Volt system in order to avoid just these problems.

The least grief and cost will come from just fitting a bigger capacity battery - but if your car starts OK then why worry?

p.s. Raising the topic of insurance in a thread for the second time today:- Modifying the electrics on your car in this way will undoubtedly make it more likely to suffer an fire through electrical fault, and being a modification from standard your insurance company could just walk away.
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Peter

[denis]

If you go for a split charge system how do you link the bateries together to provide more power ?

[Peterjday]

Care needs to be taken when using the term "split charge relay". It is usually applied to caravan type applications where the relay in question connects the "leisure battery" to the car's battery when the engine is running and isolates the leisure battery when the engine is off. The leisure battery is then used to run the TV, caravan lights and so on and it is recharged the next time the car's engine is started.

This type of split charge relay is unsuitable for Astroman's needs for two reasons:
1) The second battery isn't in circuit until the engine is actually running.
2) The relay is designed to take charging currents, not the sort of current taken by a starter motor.

I suspect that somewhere out there on the web somebody is selling kit designed to meet Astroman's desires. I can only suggest a search to find out.
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Peter

[Lynn Johnson]

sorry Peterjday I disagree with you about parallel batts, many of our farm vehicles have this set up, Tractors ,combines, pumps ,gensets etc I do agree that the batts must be as a matched pair, as for the uk spec trooper with twin batts..........

" but if your car starts OK then why worry? " very true "if it aint fixed don't break it 1 "


Lynn

[Philp]

How about replacing the current battery with an Optima gel battery, I think it's the red top one you need as a main battery and they put out a pretty huge cranking amps and have a bigger capacity too in the same size casing as a normal lead acid battery. Pretty pricey though but the upside is they are sealed for life and as they are a gel filled battery don't leak if you roll it off-road. I have a constant battle with batteries with my Chevy as cold cranking 5.7 Litres of high compresion V8 takes a lot of juice, next time it dies I'm getting an Optima as in this country I can't get a normal battery that fits the tray with a high enough capacity. I'm using a diesel Transit one at the moment and it's just adequate.
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Phil

96 or is it a 98 Isuzu Bighorn Lotus

[Niceone]

There is a whole article on fitting a split charging system in the February issue of Land Rover Owner mag. They are using Optima batteries with the second one for running a winch. Red top for starting, Yellow top for deep-cycle auxillary use.
My Series 3 son says you can get the whole kit off e-bay for £20 odd.
Why not just buy one of these power pack engine starters

[lotustower]

Split charging suits caravans and aux like winches but does not support the current to turn the starter motor as it is only a charging cct.

A single bigger battery, if you must, and a well serviced motor with the correct oil will start every time.

Twin batts may be needed if the current drain after starting doen't allow the battery to fully recover, before the next major load. Short runs with lights, heater, seat heaters, heated mirrors, rear screen etc running will reduce the ammount of charge in the battery.

And remember on th diesels IM recommend half throttle once the plug light has gone out to start.
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LotusTower - '93 Lotus Bighorn

[jocten]

Hi Astroman???
My bighorn only had one battery which needed replacing. The motorfactor sold me a battery for the 2.8td as it was listed as a single application and was rated at 85 amphours. The Trooper 3.1 takes two batteries rated at 54 amphours each. As I don't do a lot of mileage in the winter, I usually put it on trickle charge about once a month. Always starts.
TTFN, Jock.