Battery Confusion

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ashley1

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I appreciate that this is probably a very commonly asked question but I’m a mechanical engineer not electrical and batteries confuse me !
I have a yanmar 1GM10 engine on my First 26. When I bought the boat it had two identical Numax XV24 MF Deep cycle batteries wired through a one, two or both switch. The only means of charging is from the alternator or a solar panel that I leave connected when away from the boat. There is no 240 volt supply to the boat so the lights and a couple of instruments are run from the batteries. I tend to swap around from battery one to battery two as the mood takes me.
The batteries are more than 5 years old and one has just failed. Should I dedicate the remaining battery to service duties and replace the failed battery with something else or just buy another Numax and carry on as before ?
Any advice or suggestions would be gratefully received.
 
Starting an engine requires a lot more amps than running your lights and instruments. So the ampere hours are less important than the Cold Cranking Amps (CCA) that the battery can deliver to turn the engine over. The good news is that your 1GM10 won't demand a crazy amount of amps to turn it over and, provided the engine starts well, won't take much out of the battery charge either. Your engine will be specified for a battery with CCA of 200A I believe. It won't draw that much, but that's the lowest CCA battery that you should buy. The good news is that your other Numax battery is rated as CCA of 630A, so plenty of cold cranking amps in reserve (when it was new, though it will have deteriorated by now). The even better news is that you can replace the faulty one with a much cheaper car starter battery and conserve your working Numax battery for domestic use for a while longer yet.

If you use your boat fairly lightly - weekends and maybe the odd longer trip - and keep on top of charging both batteries, the 80AH capacity of your other Numax to power your lights and instruments (I'm guessing echo sounder, log, GPS, VHF, no fridge, no telly, no radar?) should be fine, especially if you have LED bulbs or you switch to them. For comparison I used to manage a 10 day cruise in my previous 23' sailing boat on a 100AH battery with only a 30W solar panel giving it a trickle charge. My sailing was pretty basic back then!

Keeping two batteries properly charged with only a 1,2,both switch is tricky and relies on a a lot of guesswork. There are electronic devices that can do that automatically for you, but that's a whole 'nother topic
 
ashley1 said:
I appreciate that this is probably a very commonly asked question but I’m a mechanical engineer not electrical and batteries confuse me !
I have a yanmar 1GM10 engine on my First 26. When I bought the boat it had two identical Numax XV24 MF Deep cycle batteries wired through a one, two or both switch. The only means of charging is from the alternator or a solar panel that I leave connected when away from the boat. There is no 240 volt supply to the boat so the lights and a couple of instruments are run from the batteries. I tend to swap around from battery one to battery two as the mood takes me.
The batteries are more than 5 years old and one has just failed. Should I dedicate the remaining battery to service duties and replace the failed battery with something else or just buy another Numax and carry on as before ?
Any advice or suggestions would be gratefully received.
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Your batteries are not deep cycle, they are sealed lead acid "leisure" batteries. If one has failed, replace it with the same, but be prepared to replace the other one soon.

Rather than fiddling with the 1-2-B switch, at least fit a decent VSR, this will allow the alternator or the solar panel to charge both batteries, irrespective of the switch setting. Do NOT use the switch on its both setting, except for emergency starting.
 
Thanks for the replies and advice. Fitting a VSR sounds like the way to go. A quick search on the internet suggests that Durite and BEP are two fairly common makes. Are they all much the same or are there any makes to avoid. Would it be better to have two batteries the same or would that not matter with a VSR ?
 
I'd just fit a small diesel car battery to replace your dead one, Durite VSR and a Bluesea 2 battery on/off switch. Plenty of wiring diagrams available on Bluesea website.
The reason you only need a small battery for starting is that your engine may take 200amps but only for 10seconds which equals 2000 amp seconds or 0.5 amp hours.
This would be replenished in 1.1 minutes by a 30a alternator theoretically or easily in 5 minutes in the real world.
 
I agree that you only need a fairly small battery to start the engine and a VSR is a good idea. The important bit is to separate the starting and domestic systems, so you never run the starter battery down with domestic loads. If space allows, maybe a smaller starter battery would allow a bigger domestic one, which is never a bad idea - there's no substitute for amp hours!

Personally, I have a 1-2-both switch with cables suitable for starting loads from both batteries. The engine battery is connected to terminal 1, domestic to 2 and the starter and "ignition" wiring to Common. This allows me to isolate the engine on the 0 position, use 1 for normal use, starting & running on the engine battery, 2 is for emergency starting from the domestic and both allows me to put them in parallel, though I've never needed to do this in more than 15 years. My split charging relay is a simple headlamp relay that connects 1 & 2. A VSR would be better for that, and I'll probably fit one when it dies, but when I set it up, VSRs were out of range of my budget.

You don't say what you have in the way of solar panels, so I'm guessing it's a small trickle charger. While you're messing around with your systems, it's worth considering an upgrade to the solar bit. I have two 20w panels, mainly because that was what I could fit on my hatch garage, the only practical place for them, run through a twin battery controller, one of these: https://www.sunstore.co.uk/product/ep-solar-duo-battery-solar-charge-controller-12-24v-10a/. It's set to charge up the starter battery first then, when that's fully charged, to charge the domestic battery. In the summer, the panels keep up with my needs at anchor as long as I don't run the cold box much (a power-hungry Peltier effect one) and, even in winter, I can stay on board working for a weekend and everything's fully charged when I come back the next weekend. An MPPT controller is more efficient, but twin battery ones seem to be harder to come by and are significantly more expensive if you do find one
 
ghostlymoron said:
https://www.bluesea.com/products/601I like these battery switches which switch two batteries but keep them isolated whilst allowing them to combine in an emergency. 1/m-Series_Mini_Dual_Circuit_Plus_Battery_Switch_-_Red
Unfortunately they're a bit pricey but look neater than two separate isolators.
Click to expand...

That switch is better than a 1-1-B switch, but it doesn't allow isolation of a faulty battery. Separate on/off switches is the better solution.
 
Stemar said:
Personally, I have a 1-2-both switch with cables suitable for starting loads from both batteries. The engine battery is connected to terminal 1, domestic to 2 and the starter and "ignition" wiring to Common. This allows me to isolate the engine on the 0 position, use 1 for normal use, starting & running on the engine battery, 2 is for emergency starting from the domestic and both allows me to put them in parallel, though I've never needed to do this in more than 15 years.
Click to expand...

Where are the domestic circuits connected ?
 
My 1GM takes a peak current of 80A and starts in under 2 seconds. When the main batteries were removed I started it with a 24Ah gel battery out of a defunct UPS with no problem. Any battery you put in will start the engine so you need to decide if you want to save money and put in a small car battery or spend more and give yourself some extra capacity to back up the house battery. As both your batteries are probably the same age the other one will probably fail soon so it might be better to get a a decent deep cycle battery now which will enable you to keep sailing on one battery when the second original one fails.
If you do end up with 2 x 100Ah batteries you need to consider how long it would take to charge them with a 30A alternator. I would guess two days of motoring.
 
I have a Parker 275 with a 1GM10. Looking for more domestic battery capacity, I ended up paralleling the two 110AH leisure batteries, and fitting a small AGM battery for engine start use. I used a 20AH Varley Red Top, which can be installed anywhere you can find space and in any orientation. This set up has been working well since 2013.

Afraid I still just have a 1-B-2 switch, but that microprocessor controlled relay looks interesting.

The boat lives on a swinging mooring, and the 20W solar cell generally keeps both 1 & 2 batteries at float voltage. The engine battery does not see too much use apart from the periodic initial start followed by 10 minutes or so of charging on the engine, most engine starts are off the domestic battery. I have an Adverc alternator controller to improve the alternator charging.
 
Thanks to everyone for all the help and suggestions. Plenty of information there to digest and then plan a way forward. Thanks again.
 
I don't know if you're being ironic, Paul, but it has been known for an item to be marketed with a different name only. I think it's called badge engineering. The eBay one is half price (and Battery Megastore is currently out of stock anyway.)
PaulRainbow said:
Tut tut Brian, you know perfectly well that it isn't the same. Do you see a Victron label on it ? :):)
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ghostlymoron said:
I don't know if you're being ironic, Paul, but it has been known for an item to be marketed with a different name only. I think it's called badge engineering. The eBay one is half price (and Battery Megastore is currently out of stock anyway.)
Click to expand...

A friend of mine used to import computers from China. He asked what name was on the label and he was asked "what name do you wont on the label.
 
PaulRainbow said:
Tut tut Brian, you know perfectly well that it isn't the same. Do you see a Victron label on it ? :):)
Click to expand...

I gave up making battery chargers because everybody started buying from China with their name stuck on, it was no longer worth trying to compete. I could buy VSR's from China with my name on, but I started designing them in the 1970's, still enjoy playing with them. and do not need to worry if people buy one or not anymore.

It's what the UK has become, buy cheap sell for what you can market it for.

Brian
 
halcyon said:
It's what the UK has become, buy cheap sell for what you can market it for.Brian
Click to expand...

I often wonder how what's left of our industry is going to survive. It's a crazy situation when the cost of a router bit/cutter including postage from China, is cheaper than just the postage and packing for the same item (costing three or four times the price) sourced in the UK.
 
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