Mixing batteries

[ditchcrawler]

My boat has the usual engine & domestic batteries with a one/two/both switch.They are both Sonnenschein gel batteries of some 6 or 7 years age.The domestic one shows 12.8 volts at rest,but the engine start one shows 12.2 volts & after a week will not turn over the engine(a Nanni 2.5HE 14 HP).I assume it is defunct.The question is do I need to buy a replacement gel battery(expensive) or can I buy a cheaper engine battery & replace the domestic battery later with a non gel.I am tempted by the Redflash micro engine battery,although it cannot (I understand) be used for anything other than engine starting.Can I mix say a Delphi engine battery or a good heavy duty dual purpose engine battery with the gel domestic or will it cock up the charging regime.Is there a definitive right or wrong in this situation.

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[Talbot]

IIRC the gel batteries take a higher charging voltage than lead acid. Is your charger set up for gel bbatteries, if it doesnt have a setting for this then it wont matter (but probably better to charge seperately rather than using the Both switch) Even if it does have this ability, switch between the settings and the battery switch to select correct regime for correct battery.

Suspect that gel batteries are rather like deep cycle ones, they are not designed for heavy cranking loads, and thus using them for engine starting is a good way to kill them early.

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[boatmike]

Agreed. Most gel batteries are deep cycle. Not designed for high cranking loads. You can do no better for engine starting than a good old wet cell lorry battery for cranking assuming you are not constantly at a wild angle. Of course if you only have half a boat rather than a proper catamaran the angle of dangle is a consideration! The commonly sold "leisure" batteries are a reasonable compromise between high cranking loads taken for short periods and deep cycle batteries designed for relatively low load over long periods but nowt does both well. There is also a spiral wound battery sold by Bardens that is possible to be used for both but frankly you dont need the expense unless you feel a wet acid battery will spill. Wet batteries will (especially with a smart charger) take a high charge rate better than gel batteries so why not change both and switch over?
No harm in mixing them but you wont get maximum charge rate to the cranking battery for best effect
<hr width=100% size=1><P ID="edit"><FONT SIZE=-1>Edited by boatmike on 15/10/2004 12:26 (server time).</FONT></P>

 

[Talbot]

There is another type of battery that is worthy of consideration, and that is the carbon Fibre reinforced ones batteries. They can withstand much higher charging currents than traditional lead acid batteries. Due to the high inherent strength of the Carbon Fibres used, the plates are mechanically very strong. The Fibres are very conductive, allowing much higher charging currents to flow deeper into the battery plates.

More info <A target="_blank" HREF=http://www.elecsol.com/html/products.html>here</A>

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[boatmike]

These are the same as the spiral wound ones I suggested from Bardens but bigger and heavier for the same performance. I think they are cheaper though.

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[Talbot]

No they are different design. The optima are designed to achieve high CCA for engine start, whereas the Elecsol produce a lower CCA rating, but are more dual purpose, and can also be used as deep cycle

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[JackFrobisher]

I changed from two "leisure" batteries to one deep-cycle and one cranking during the summer. I can't comment on the technicalities of gel, non-gel etc. but it's very clear that the engine starts much more easily on the cranking battery and the fridge can run for longer on the deep-cycle battery without knocking the voltage down like the old ones. I'd recommend a mix, based on the two types.


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[boatmike]

No they are of similar design the difference being that the Optima will achieve superior cranking performance. The deep cycle performance is very similar. Optima are as I said more expensive though and lighter so you pays yer money and takes yer choice.

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[dickh]

When I got my boat 7 years ago, It had two Sonneschein Gel 110AH Batteries which were used for both engine starting & domestics. They both died on me and after finding out the cost of replacements I opted for Exide 110AH Marine dual purpose batteries at about ¼ of the cost. Work well and I now don't get flat batteries. Go for a Heavy Duty Car battery for engine starting and a Wet lead acid for the domestics.

<hr width=100% size=1>dickh
I'd rather be sailing... /forums/images/icons/smile.gif

 

[bedouin]

Mixing batteries should not be a problem provided that you don't keep them paralleled up (in the both position) without the engine running.

Having done a lot of research into this recently I came to the conclusion that for the average boater there was nothing better than the cheapest "wet" leisure batteries - which also have the advantage that with a smart charger they can be charged faster than any other type.

Easiest solution is to go to Halfords and buy a cheap car battery for engine starting. I've also been tempted by the redflash, but I haven't yet worked out how to solve the issues about charging it...

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[halcyon]

What issues do you have charging redflash ??
Seams resonably simple.

Brian

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[bedouin]

There are two things about recharging the Red Flash that concern me. Firstly my domestics are el-cheapo flooded lead acid - which means they can be charged at 14.8V and the electrolyte topped up as required. No sealed battery will take that voltage.

Secondly, starting the battery takes very few Ah out of the starter battery, and that charge is probably put back within 5-10 mins. Even if I were to reduce the charging voltage to 14.4V I am still not convinced that the Redflash would be happy having 14.4V applied in its fully charged state for hours on end.

I've been considering options for either reducing the charging voltage to the RedFlash or for disconnecting the RedFlash from the charging circuit once recharged (part of a conventional split charge relay set up).

Incidentally these cheap portable "PowerPacks" use a 17Ah golf-cart battery which costs a fraction of the cost of the RedFlash. I have also wondered about trying one of those, but I'm not sure it would take the strain of being used regularly to start the engine.

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[Evadne]

Having minimal non-engine electronics I've done this for years now, and can recommend it. Running a VHF and occasional nav. lights over and above the engine duties does not sem to tax a simple wet-cell battery. If you have things like a fridge or a radar, which have a significant draw over a 24 hour period, then you may benefit form a deep cycle battery. Remember though, that the lifetime curves of a bog-standard ATS/Halfords and a Ripoff Inc. Marine lesiure battery will converge if you discharge the battery too much. I understand Deep cycle to mean more than 25% of capacity between charges, whereas 33-50% of capacity is a good way to knacker the poor thing rapidly.

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[pvb]

That\'s sensible advice...

The Nanni 2.5HE is less than 0.5litre displacement, and it only needs an ordinary (and fairly small) car battery to start it. The Redflash would be a waste of money unless space and weight considerations are really important.



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[bedouin]

Re: That\'s sensible advice...

For me the space is a consideration. It is not easy to fit another full-size battery close enough to act as an engine battery. The small red flash take up very little space and would enable me to use my current engine battery to double the domestic capacity.

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[boatmike]

No it wouldn't.
These are "traction" batteries and more akin to your deep cycle battery than a cranking battery

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[FullCircle]

Nobody has admitted to being as cheapskate as me yet. I get mine second hand from breakers etc. With the value of cars at diddly squat in ten years, most cars have a reasonable battery, which can be had for a fiver a go. I have an assortment of different battery terminal connections, and I usually stick in the 55Ah to 85Ah size bracket. They usually last more than a season (this last pair are now 2 seasons old), and I keep them on Optimate for the winter. I have a 5A (yes!!) alternator on board and a 5w solar thingy. Keep a sketch of the battery sizes about you and Robert is your Fathers Brother.
If not, then visit Battman.co.uk who is damn cheap and gets them delivered to your door. Good service (no relation)

Jim
Feeling Tight Again

<hr width=100% size=1>Engine now resembles Singer Sewing Machine - amazing what happens when you renew all the old bits.

 

[bbilly]

Re: That\'s sensible advice...

Bedouin - Ive got the same concerns. I have to optimize space and have a redflash as an emergency starter battery. At the moment its tucked away until ever needed but like the idea of using it as a permanenet starter and change the current starter battery to a deepcycle for a coolbox. Any hints on how to charge a deepcycle and a redflash from one alternator, what gear, circuit diagram?

Thanks in advance

Will

<hr width=100% size=1>"If you're too open minded your brains fall out"

 

[pvb]

Simplest solution...

Your simplest solution, Will, would be to use a VSR (Voltage Sensitive Relay) to connect the Redflash starter battery to the deepcycle battery. VSRs are small, lightweight, easy to fit and reliable. Unlike diode splitter solutions, there's no voltage drop involved. When you start the engine, as soon as the starter battery voltage reaches 13.7v, the VSR closes and allows charging current to flow to the deepcycle battery. When you turn the engine off, the VSR opens and isolates the deepcycle battery, so that your coolbox won't discharge the starter battery. Some good VSRs are made by <A target="_blank" HREF=http://www.bepmarine.com/showproduct.cfm?productid=12>BEP Marine</A> (click on "Distributors" to see details for Italy) and their 100A version would be fine for your needs. Be sure to connect the VSR using wire which is more than adequate for the maximum current likely to flow through it - your Volvo probably has a 60A alternator, so you should size the wire to be able to cope at least with that current.

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[Guest]

Cheapskates ....

There are a few around that will definitely agree that I fall in that category without doubt.

I must remember about the batterys from breakers yards ..... good one that.

<hr width=100% size=1>Cheers Nigel http://groups.yahoo.com/group/gps-navigator/ http://groups.yahoo.com/group/searider/