DIY Battery Box

The SLA has never gotten wet, but I am still a little worried, so I'm thinking of vacuum sealing the battery.  Poke holes for the wires, seal wire holes with Goop, let dry, then vacuum seal. 

You could save some time and effort if you just threw it into a dry-bag.  But tinkering is fun.

I managed to ruin the marine plug on my current battery box, so I'm likely going to run with a drybag setup til I get down time to make a new box. 

I wanted the female adapters for easy connect/disconnect inside the box, but after still waiting on them for over 3 weeks, I think I'm just gonna skip it, at least for today and tommorrow when I need the battery.  Unfortunately, that means cutting off the male adapter.

Edit:  I'll just use the lead acid brick until I get all the parts I need.   

I just weighed the 7aH SLA and the 9.8aH Li-ion Blue Brick.

SLA:     4.96 lbs
Li-ion:   0.93 lb

My kayak just lost 4 lbs!  That's about 6%. 

Still no cctv connectors (female adapter) but the 2 prong  waterproof connecter, ordered two weeks after the adapter, has arrived.  Grrrr

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34 days later, the cctv female adapters showed up.

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I mentioned this in another thread, but here it is more appropriate. 

I was worried that the new "blue brick" Li-ion battery was not particularly water resistant/proof.  The switch, the cable entry point, and the shrink wrap were all points of entry.  My original SLA was held in the rear gear bucket of the Revo and never showed a sign of getting wet, but the SLA is "sealed" by definition and in reality. 

I vacuum sealed the blue brick.  Punched a small hole in the bottom of the bag and threaded the cables through the hole.  Then a copious amount of silicon seal was used to seal the hole and cables.  The seal was allowed to dry for a few days then I vacuum sealed the battery.  The switch can still be used.  The last thing I need to do is find some sort of water proof cap for the charging cable connector.

Ordered a blue brick as a back up so I guess I'll be ready to pimp it in a month. Nice find Craig!

The brick will show up in 2 weeks or less.   

I have got to say, "THANK YOU!" to CraigVM62 for the blue-brick battery and 2-pin waterproof connector ideas.

I've completely rewired the Revo using both and abandoned the so-called Marine Grade Power Plug.  Since the blue-brick has an integral on-off switch I just wired the battery direct to the power on the FF connector with a couple of those 2-pin connectors.  Shrink-wrapped with Goop at the ends of the shrink-wrap and I am waterproof.  Lightened the rear of the boat, the end I have to lift, by 4 pounds.  This may not sound like much but it is 6% of the hull weight.  Life is good.

Thanks, Craig!

I also remounted the transducer with a DuctSeal ring and water.  Looks very promising, no seepage under the ring for over a week.  Transducer is held in place by carefully compressing the putty onto the transducer.  Ring is filled with fresh water from a 25ml syringe sans needle.  Will report on performance Tuesday or Wednesday. 

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=220857050716

FYI, ordered one for Linglady today, and current prices is $35.99 with free shipping.  9800 mah lithium battery with charger. 

Having used the blue-brick as power for my FF/GPS on 4 trips, I have an observation.  My previous SLA required about the same amount of time to charge as to discharge, so it I ran it for 6 hours it took about 6 hours to charge it back up.  Not so with the blue-brick and charger I have.

I got the 9.8Ah unit which came with a 350mA (max current) charger.  I charged the battery after each trip, yet after just 3 hours on the last trip I got a low voltage warning from my FF/GPS at 9V.  This was about 15 hours of total run time with charging in-between. 

After thinking about it and reviewing the charging characteristics of Li-ion batteries, I realized it takes A LONG time to charge the battery with the supplied charger.

Let's say I have drawn the battery down by 70%, that is, I've pulled 6.8 Ah out of it.  If the charging efficiency is 100%, then using the supplied 350mA charger will take about 19 hours!  However looking at the charge curve it looks like overall the charging cycle is about 63% efficient.  That means about 30.5 hours to charge. 

A 100% draw down would take about 45 hours.  In reality it seems to be taking longer.

I've ordered a 1500 mA intelligent charger. 

How much?

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Thanks for the feedback Demonick - your reports on gear are really worthwhile.

Li-ion batteries have a lot of good properties to recommend them, but being foolproof is not one of them. Charging requires a level of care that almost demands smart charger. SLA's are much easier for the average Joe to use. I have a 9AH that was salvaged out of a computer UPS about 8 years ago, and have used it as bicycle lighting system battery since then. It charges with a cheap 1A trickle charger, using the 1:1 discharge to charge ratio, and it is still going strong. It is way heavy, and I should get a 4AH SLA to replace it, but it was free, so I have been using it for my FF too. I am tempted by the sexiness of the the Li-ion, but I like the ruggedness of the SLA. (I also have my SLA in a drybag on deck, so I don't have to lift it with the yak.) Keep us posted on further developments.

How much?

$18/free shipping.  I hesitate to publicly post a link as I have not received and tested the unit. 

I have yet to experiment using the charger that came with the battery I picked up off ebay.  At work I charge them with a 4 output variable DC power supply with voltage dialed to 12.75 volts and amperage around 700 to 800 ma.   Because of enclosure size restrictions, I have only worked with the 6800 and 9800 mAh versions of these batteries at work.   I keep a meter on each and pull them when balanced voltage reaches around 12.60 volts.   When pulled from operations,  they are typically drained down to around 10.5 - 11 volts and take around 8 hours to charge back up.

Demonick
 I believe I am getting these charge times because of the higher amperage that I am charging them at.  Could you post the specs of the charger you ordered.   It has been years since I seriously dealt with batteries and charging techniques, back when I was into RC racing.   We are talking NiCad days so my knowledge is likely way outdated.

I will experiment by draining one of these batteries to the point that the built in regulator releases / shuts it down.  I will then charge it with a 1000ma / 1A standard transformer and monitor the charge rate / time until the built in regulator disconnects again.    I also have access to so real hardcore bench techs and will see if they can help bring me up to speed.

         
   
 

Got my blue brick pimped and ready to give it the test run tomorrow. Thanks for the tips DN. looking forward to the charger specs.