Dan Bartmann’s batteries

I read this facebook post by Dan Bartmann this morning and felt it was worthy of wider attention:

Facebook always asks me ‘what’s on your mind’. Lotsa stuff that I don’t wanna share. But for now BATTERIES. I’ve read lots about them… how to take care of them, I understand the complicated charge controllers available now etc.

I got mine off ebay 10 years ago… new but sitting on a shelf for way too long before I got them. Today they are as good as the day I got them. They’ve been moody in between.

My only charge controller is a Morningstar Tristar TS60 running a dump load. The dump load was a 4000 Watt heater but since the flood two years ago only about 1000W of it comes on sometimes. Easy fix, not done yet. (just saying the charge control on my battery is mostly about boiling off water and there’s not much electronics involved)

I water the battery fairly quarterly and everytime I do I add way too much. (7 gallons last march)

My low voltage cutoff on the inverter is set to 32 V (because there’s times when I ask my battery for the very last drop)

So why is it that today and recently its cloudy, not windy… I’m sitting at 50V with a tube amp and the internet on and I just ran a well pump for a while and it’s all good? This is a Forklift battery I got off ebay 10 years ago. It probably needs another 7 gallons of water haven’t checked recently.

I think to a battery years are less than dog years (human x 7) I suppose I take care of myself as well as I do my battery maybe a little better. I should live to be 150.

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3 Responses to Dan Bartmann’s batteries

  1. David Simms says:

    I guess that Dan’s pretty happy with his batteries but I think he could be a whole lot happier if he got his dump load fixed up properly.
    This is a bit beside the point but, over the past few years, I’ve designed a nice PWM regulator that has been in use continually. When I see some behaviour I believe can be improved, I pull out the PIC and re-program it.
    With PWM regulators, the rule-of-thumb is to have a dump load equal to the maximum input wattage from your solar, wind, or whatever. If the dump load is larger, that’s no problem, as long as you stay within the instantaneous current switching capacity of the regulator. However, when the wattage of the dump load is less than the potential input from the source(s) what can happen is this; your duty cycle will rise to the design maximum, close to 100%, then the regulation will be insufficient to prevent the battery voltage from rising. As a result, the battery voltage will rise and it will exceed the recommended float voltage.
    Well, if you’ve got a large battery this may not be too too serious but, you’ve got to go back to the current specs of the manufacturer which specify the float current, etc…The fact is that allowing the battery voltage to go beyond the recommendations will lead to greater water consumption, as Dan has alluded, but it can also lead to the shedding of active material from the plates. Over time, this material will accumulate in the bottom of the cases and, one day it could short out the cell(s). Another sneaky effect it could precipitate is that the increased water consumption could drop the electrolyte level below the tops of the plates…if the cells aren’t being supervised. This will cause erratic battery performance.
    So, …message to Dan…fix your dump load and remain happy, happy…or else. Batteries can last a good long time if treated right.

    • admin says:

      Hi David,
      Yes, Dan is a bit of a rule breaker, but it’s interesting. The type of battery he is using is very robust and thrives on being charged hard.
      Battery management is partly a matter of personality. I always laughed a bit at the solemn articles about how to manage solar pv systems where they set the charge controller to limit the voltage day after day and then at a certain pre-ordained time they start and run a petrol generator all day to charge the battery to a higher voltage so as to equalise. Why not let the renewables equalise the battery?
      With wind systems the availability of charge tends to be a lot more random than with pv. When there is plenty of wind it is good to push the voltage up pretty high. If Dan had a hydro system his batteries would be exploded long ago but in his situation with intermittent power, and robust battery plates, the way he treats them actually makes quite good sense.
      cheers
      Hugh

      • David Simms says:

        Yea, Hugh, some of those systems are pretty anal, programmed a certain way, just because it’s possible to do so. I agree, about forklift batteries but the conservationist within me really wants to treat batteries well because they’re such a fundamental, and expensive part of any system.
        When running my wind system, I had a beautiful set of 760A-H ex-telephone exchange batteries (lead calcium). They were designed for float service but, in my unregulated wind system -we’d either turn off the mill or turn on all the lights we could, all incandescent, to keep the volyage down. But, that wasn’t the downfall of the batteries, over-discharging was. Anyway, they still lasted seven years.
        You’re point about persistently float charging solar batteries hits the nail on the head. Our batteries need a bit of stirring up to burn off the sulphates and to keep the electrolyte from stratifying. In my little regulator, I allow the system to head toward 30 volts 29.6 actually) before slipping into float. Then, it locks in the float parameters for 3 hours, after which it will, again, allow the volotage to rise momentarily. The strategy seems to be working well and water consumption isn’t a problem. I water 2-3 times a year.
        It’s all great fun, keeping us from getting into other kinds of trouble. I like the idea of doing the most with the least and getting stuff to last a long time. I’ve seen too many systems that are either totally abused or that are far too dependent on gas generators….I hate the things. I wonder whther Dan is still using his steam-powered backup generator…

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