Tai 13 Posted February 8, 2022 Author Share Posted February 8, 2022 Thanks all, some good insights! For now I think I will just keep the current switching setup and replace one of the starts with a deep cycle. Last question I think! I have been running the house charge via alternator with out the start battery connected i.e after starting and running for a while, I switch the house in and then the start off. Is this OK? Or is just better to leave them both connected in parallel, even when the house is run down? Quote Link to post Share on other sites
aardvarkash10 954 Posted February 8, 2022 Share Posted February 8, 2022 1 hour ago, Tai said: Thanks all, some good insights! For now I think I will just keep the current switching setup and replace one of the starts with a deep cycle. Last question I think! I have been running the house charge via alternator with out the start battery connected i.e after starting and running for a while, I switch the house in and then the start off. Is this OK? Or is just better to leave them both connected in parallel, even when the house is run down? put solar on the house battery - size dependent on your loads, but our unoptimised (points the wrong way, under the boom) 130W panel keeps up charging our 105Ah house battery running an isotherm fridge, stereo, LED lights, VHF, and anchor light. Connect the batteries when the engine is running, disconnect them when the engine is off, connect them when you are not using the boat so the solar maintains both batteries. 1 Quote Link to post Share on other sites
CarpeDiem 430 Posted February 8, 2022 Share Posted February 8, 2022 5 hours ago, Tai said: I have been running the house charge via alternator with out the start battery connected i.e after starting and running for a while, I switch the house in and then the start off. Is this OK? Or is just better to leave them both connected in parallel, even when the house is run down? Yes it's fine to leave them both connected while the engine is running. In fact I would recommend it. 4 hours ago, aardvarkash10 said: connect them when you are not using the boat so the solar maintains both batteries. I recommend against this. Because 1. overnight there will be no charge source and you'll have two different batteries connected in parallel 2. If your house is lower than the start (which is likely) when connecting them in parallel, there will be an inrush from the start to the house. If done repeatedly this will cause your start to degrade. Quote Link to post Share on other sites
aardvarkash10 954 Posted February 8, 2022 Share Posted February 8, 2022 31 minutes ago, CarpeDiem said: 2. If your house is lower than the start (which is likely) when connecting them in parallel, there will be an inrush from the start to the house. If done repeatedly this will cause your start to degrade. I agree its a theoretical issue, but after 40 years in and out of autoelectrical trades, I haven't come across it as a practical problem of any consequence. For us, we start any trip on the motor, up to 30 - 45 minutes getting out of or into the river, otherwise about 10 minutes motoring on arrival at or leaving an anchorage and getting sails up. The batteries are not big and are relatively similar in capacity by cruising standards - the start is about 70a/h, the house is 105a/h. If the difference was much greater and/or the battery banks were larger, yeah I'd take a different approach. 1 Quote Link to post Share on other sites
wheels 543 Posted February 8, 2022 Share Posted February 8, 2022 10 hours ago, aardvarkash10 said: I agree its a theoretical issue, but after 40 years in and out of autoelectrical trades, I haven't come across it as a practical problem of any consequence. Ha, reminds me of a time I was telling a guy about Battery care. His boat had one start battery also being used as house. I gave a great speach I thought. At the end of it all, he said, well this battery is now 10yrs old and still working fine. How much longer would I expect from it if I had done everything you just said. That stopped me in my tracks. It was a cheap start batter and shouldn't have lasted the time it did even if it only ever was used as just a start battery. But in saying that. Don't take it as an excuse to not follow the proper battery rules, just because one situation was out of the norm and worked. 1 1 Quote Link to post Share on other sites
Psyche 626 Posted February 8, 2022 Share Posted February 8, 2022 Classic! Still, if you happen to have a 500-1000 dollars in batteries (easy) or more common than you think, 5-10k you really want to take care of them. A guy near me spent 7k on a lithium setup and for some reason he had to do it again within 18 months, ouch. Quote Link to post Share on other sites
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