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Author Topic: Hydometers  (Read 8791 times)
Alba
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« on: August 31, 2012, 03:41:50 PM »

Hi All !

Can anyone tell me where to buy a good/accurate hydrometer and should I invest in a digital temp comp one for ease of use ??

Ali
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camillitech
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« Reply #1 on: August 31, 2012, 06:44:32 PM »

Hi Ali, I've been through dozens, it does not matter whether you pay 3 or 40 they're all more about comparisons than accuracy.

I've got this one at 40



http://www.thetoolboxshop.com/0-472-00-durite-precision-battery-hydrometer-3198-p.asp

and this one for



6.50

http://www.thetoolboxshop.com/61792-draper-tools-battery-hydrometer-3228-p.asp

and all manner in between. To be perfectly honest the Draper one is the best I've used as it's the only one that has not split and cracked after a couple of years.

We have five at work and I swear they all read different  Roll Eyes

Never tried an electronic one right enough.

Cheers, Paul

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'Off grid' since 1985,  Proven 2.5kW, Proven 6kW direct heating, SI6.OH, 800ah Rolls, 4.75kW PV ,4xTS45, Lister HR2 12kW, , Powerspout pelton, Stream Engine turgo, 60 x Navitron toobs and a 1500lt store. Outback VFX3048 and 950ah forklifts for backup,
Alba
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« Reply #2 on: September 01, 2012, 06:19:47 PM »

Thanks Paul

I broke one similar to the photos 3 months ago and never replaced it  whistlie

Ali
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Alba
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« Reply #3 on: September 08, 2012, 06:38:25 AM »

Ok Ok, plenty of  Roll Eyes Roll Eyes and some  facepalm will be accepted from the seasoned off gridders.
Picked up a cheap hydrometer last week like the ones you posted Paul. Just as well, I measured all the cells after an absorb(100w load)and some SG's were as low as 1.225. I equalized them for 5 hrs and while some cells were happily sitting at 1.265 - 1.275 the worst offenders only rose to 1.240. There was a lot of murky grey electrolyte in quite a few cells but thats a good sign that things are getting mixed up well. So, after a week of loooong...... loooong absorbs @ 59v things are starting to look peachy once more  whistlie
Just waiting for a clear sunny day. I'll use the genny(it's needing a complete rebuild/replacement but thats another story banghead) to get to the end of absorb stage then cook, hrrm, equalize for a good 4- 5 hrs or as long as is needed to level out all SG's.
Thanks Paul, for like you said, a cheap hydrometer is good enough for comparing cell SG's and  fingers crossed! the batteries havn't been permanently damaged by the stupidity of the off grid newbie
Ahh, there is nothing better than feckin around with SG's while trying to celebrate your 1st anniversary as an off gridder  bike

Ali
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stephendv
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« Reply #4 on: September 08, 2012, 08:19:40 AM »

Congrats Alba!
Didn't see this post earlier, but I have this one which I really like because of the ease of use and reading it: http://prismsolar.co.uk/shop/index.php?_a=product&product_id=86
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camillitech
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« Reply #5 on: September 08, 2012, 08:36:52 AM »

Well spotted Ali,

I cannot overemphasize the importance of regular SG checks, I used to do my weekly and log them but now I do it monthly unless one starts to misbehave. I seem to spend half my life checking SG's but it's always paid off.

Cheers, Paul
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'Off grid' since 1985,  Proven 2.5kW, Proven 6kW direct heating, SI6.OH, 800ah Rolls, 4.75kW PV ,4xTS45, Lister HR2 12kW, , Powerspout pelton, Stream Engine turgo, 60 x Navitron toobs and a 1500lt store. Outback VFX3048 and 950ah forklifts for backup,
Alba
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« Reply #6 on: September 09, 2012, 09:11:50 AM »

Stephen, that looks a neat piece of kit. I got a bit worried when I seen the Outback and Surette prices that maybe I paid OTT here in Finland but after checking, it wasn't too bad.
Paul, I've learned my lesson and hopefully no permanent damage done. I felt a bit quilty of neglect on my little red babies so yesterday, disconnected everything and started on the insulated batt box. 5cm styrox, 2x2's for the batts to sit on. I'll clad the sides and line with the styrox and make a similar insulated lid with vents. Forgot how heavy a 100kilo battery was and nearly gave myself a hernia in the process facepalm



I need to warm it up a bit for the winter, -40c is not uncommon  freeze I know LEDs get hot, well the heatsink on my headlamps does, so I was thinking of 5w of LED but would a 5w strip of LEDs be better than a single 5w bulb. Not sure if the strip with approx 20 small bulbs will produce the same heat a the single one.
Any ideas, suggestions or than moving to warmer climes ?

Ali
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A.L.
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« Reply #7 on: September 09, 2012, 09:52:54 AM »

hello,

Quote
Any ideas, suggestions or than moving to warmer climes ?

 - trace heating? - en.wikipedia.org/wiki/Trace_heating
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Alba
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« Reply #8 on: September 09, 2012, 02:40:59 PM »

thanks for the suggestion A.L I have 2 trace heating systems in my water feed pipes that supply the house and kota. While they work extremely well keeping cold water above freezing point, I believe the power usage would be too great to keep a battery box warm with ambient temps @ -10 to -40c. I have read of people using an incandecent 40w bulb but that would be approx .8kwh. If LED would work, that would only be .1kwh  fingers crossed!

Ali
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A.L.
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« Reply #9 on: September 09, 2012, 03:53:37 PM »

hello again,

thanks for the suggestion A.L I have 2 trace heating systems in my water feed pipes that supply the house and kota. While they work extremely well keeping cold water above freezing point, I believe the power usage would be too great to keep a battery box warm with ambient temps @ -10 to -40c. I have read of people using an incandecent 40w bulb but that would be approx .8kwh. If LED would work, that would only be .1kwh  fingers crossed!

Ali

Sorry, but I have to disagree, it will take a fixed amount of energy/heat to keep an object a certain temperature above ambient regardless of the source of that energy/heat.
Indeed if any of the light escapes you will have to supply more energy.
Having the heat source below the batteries will ensure the most effective use on any input energy and a thermostat will prevent overheating. If the heat source is above the batteries it would encourage convection currents and increase heat loss from the box

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Gambot
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« Reply #10 on: September 09, 2012, 04:50:02 PM »

I need to warm it up a bit for the winter, -40c is not uncommon freeze I know LEDs get hot, well the heatsink on my headlamps does, so I was thinking of 5w of LED but would a 5w strip of LEDs be better than a single 5w bulb. Not sure if the strip with approx 20 small bulbs will produce the same heat a the single one.
Any ideas, suggestions or than moving to warmer climes ?
LEDs consume low power because they are efficient light generators as most of the power they consume is converted to light and not heat, whereas incandescent bulbs produce more heat than light.
Car LED headlights have a heat sink because they are pushing high wattage through a tiny junction(s) which cannot be allowed to get too hot or it will self destruct.
So LEDs are no good as a heat source.  
« Last Edit: September 09, 2012, 04:52:28 PM by Gambot » Logged

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marcus
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« Reply #11 on: September 09, 2012, 09:10:07 PM »

how long does it stay that cold? If it just dips occasionally and trace heating is too power hungry then add some thermal mass around the batteries - water in conical containers (so they don't split) will hold the temp at 0C whilst it freezes, and when you've got a surplus of RE coming in, dump the excess into the heaters to bring the water back up to 20C

Or more insulation of course.
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stephendv
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« Reply #12 on: September 09, 2012, 09:54:33 PM »

With a good amount of insulation, won't the daily charging and discharging generate enough heat to prevent freezing?
Keeping them above 75% state of charge, on it's own should also prevent electolyte freezing according to this: http://jgdarden.com/batteryfaq/carfaq4.htm#freeze_points 


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johnrae
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« Reply #13 on: September 09, 2012, 10:02:07 PM »

If you must use a  heater, rather than a light bulb, why not use a power resistor.  Say you want 10 watts of heat and you are driving it with 24 volts, then the resistor required is be derived from the equation  W=V2/R  hence R= V2/W.  
In the example case R= 24*24/10 or 57.6 ohms (preferred nominal value = 56 ohms)    If you use a wire wound 33 watt power resistor then you'll get a decent life and the approximate 10 watts you require, but with a relatively cool body - unlike a lamp bulb.   Same wattage of heat but lower temperature.

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Alba
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« Reply #14 on: September 11, 2012, 12:17:33 PM »

Thanks for all the advice guys
Talking of trace heating...... had -7c yesterday morning and the brass connection to the plastic feed pipe popped off (trace wasn't on obviously) and the trace cable had been pulled out from the feed pipe by about 20cm and for the life of me, I could not push it back in and reconnect the brass connector. Had to cut it and pull the whole 30m cable out for now till I get some new parts  banghead
Back to the batts.... I only take them down to 80% SOC, so they wont freeze, just the chemical process will be slower. The batt box is finished (well, insulated at least  whistlie) so I'll stick a thermometer in there to see what difference there is from ambient. I never feel much heat from the outside of the rolls casing but maybe the cells themselves heat up somewhat that may "see them through" till next morning.
So if heating is required, LEDs are out. I will look into some sort of "heating pad" if the consumption is low enough.

Thanks again

Ali
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