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Dr Bob

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Dr Bob last won the day on September 23 2018

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About Dr Bob

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  1. It does look a bit small doesn't it. Honest guv, it is 90A. The 50A starter alternator is smaller. Anyone know what make it is? Its the bog standard one supplied with the beta 43.
  2. Tumshie' bald as well. So's my alternator.
  3. Ah, I see. Its in the engine hole on a cruiser stern so not easy to reduce the heat without installing fans. The skin tank is on the other side of the engine. Yes I could put a fan on it and I am sure it would cool it. The alternator is near a bulk head so that would make it relatively simple. I will be very happy if I can run at 55A. Can you buy a magnetic one?
  4. ....but have you measured it with an infrequent red thermometer? Every boat should have one!
  5. That problem was on the starter battery alternator (a 50A one) that the AtoB was using all the time rather than sharing the duty with both alternators. I just disconnected the 50A one from the AtoB and wired it direct to the starter battery so no problem. It is interesting that that problem had the 50A alternator operating at 50A output all the time ......and the alternator ran at 90°C. It was like that for a month or two and hasnt suffered. Been fine for the last 8 months.
  6. See my response to Rusty a few posts of mine before. I can reduce alt output to 45A which keeps me below 80C on the hottest bit but that was the point of the OP....am I safe at 90C? It is obvious that you cant run a 90A alternator at max output for any length of time but I cant see any info on just how much you need to reduce it to get good life. The Balmar site discusses it in detail and shows how their system reduces output via their belt manager system but that doesnt give info on what typically the current is reduced to - they just talk about %'ages but % of what? I guess 45A on a 90A alternator should be fine for 2-3 hours......but is 55A.
  7. I think the quick answer is none......well actually lots. There are 4 settings (dip switches) on the AtoB that are for different battery types. On Lead acids, these give absorption voltages from 14.0V to 14.6V and the current levels on initial charge increases from 40A to 60A across the 4 types. I am using this to give me a bit of control over the lithiums. On the US Gel battery setting, the LA absorption voltage is 14.0V. On the lithiums, it looks like this will be the termiinating voltage for 100% charge and it gives me 45A output...all the way to 95% charge (not been to 100% yet). On the gel setting I get 55A and voltage seems to be 0.1V more. So yes, the AtoB is the thing with which I can control the current and 45A looks ok for temp but 55A was getting to 90°C...hence my question. I will stick to the 45A for now as I want to check out the termination voltage but may they go to the 55A.
  8. Thanks JTN. I had seen that data before. The question though is where are they measuring the temperature? The temp on mine varies from 50 to 90 across the top (from back to front). It is good to see that they are quoting data at 93C as that means they must be anticipating it operating at that temp....but then again ....which part of the alternator is at 93°C. Same for chemical reactions. 10°C doubles the reaction rate.
  9. Thanks Dave, That's a bit more confidence that I am ok at the current temperatures.
  10. Thanks Tony, yes I will ensure I keep the amps down. I think 55A amps is probably the most I will try initially and likely 45A if doing long days.
  11. Must have been reading this thread.
  12. .....bloody BMW? It would probably break down again and need a new BMS.
  13. Thankyou MP. I now understand what you are doing. Yes, quite complex. Your system is good for this as you can measure and record the individual cell data and then pick and choose which data you want to use to compute - unlike mine where I am stuck with recording just overall voltage data but perhaps slightly more accurate current and amp hours used - but then cant use it in real time. I am going to try and graph my data and produce a set of volts v SoC at varying small loads/charging and then see over the next few months how that lines up with the SoC prediction from the BMV.
  14. This is for cell voltage on a big charge or a big discharge. I dont recognise the shape as I have not yet plotted cell voltage with SoC. If however you just look at total bank voltage you see a different picture. I will try and find time next week to plot what I am getting but it seems from just looking (not graphed it yet) the data that it is a straight line from 12.8V to 13.3V from 40% to 90% SoC - IF you are not charging or discharging over 10A. Loads of 1A to 10A give a drop in voltage of say 0.01-0.05V only. Solar at 1A to 10A charge gives increase in voltage of the same amount. Charging at 50A increases an at rest voltage of say 13.3V to 13.8V so as MP says, ignore voltage when charging (other than to see the voltage termination point) or give it a 10 mins or so to drop. It will be easy just to eyeball the voltage as long as the load isnt too high and estimate SoC. I will do a graph next week once I have had chance to look at the data.
  15. Thanks Tony, catweasle and Bizz. Ok good to know the diodes are at the back and that's where the cooling is coming in. Yes it will be hotter in the summer - I hope! I will keep an eye on temps and restrict to charging at no more than 55A for now.
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