Installing an extra battery

[Simon]

Hi guys,

I'm going to install an extra battery in one of my pannier boxes which will be switched. I'll switch it on about once a week to give it a charge, but most of the time it will be isolated so that I have a ready to use boost start option - simply flick the isolator switch and I am instantly connected to a back up battery for the times when the bike has need standing and the alarm and clock have drained my main battery.

Anyway, since this is only a backup battery I don't want to spend too much money on it - can anyone recommend what kind of amps output I need to buy to give me enough power for an emergency jump start situation?

S

 

[T_C]

For simplicity, easiest to probably just use a direct replacement battery. The you can swap it out with your main when it dies. If you drain the main battery often due to alarm or whatnot, it will probably have a short life. Be sure to use a battery isolator switch.
T

 

[2thdr]

First time I've ever heard of someone doing this. Had two battery bank on my sailboat...but not on my bikes. Maybe somebody will chime in...

Sent from my DROIDX using Tapatalk 2

 

[SteveST1300]

I would say be careful the weight of the battery may break the plastic in the pannier. If you are going to run a second battery you may want to go with a lithium iron ans they only weigh 2lbs.

 

[st1300r]

Search the site there were a few threads on this.
iirc 1 was a lithium iron stuffed in the tail not the saddle bag.

.02 fix whatever is draining your battery. It isn't helping it's longevity.
stock (here without hss) quiescent drain is something like 2.5ma

 

[sennister]

I think there is some stuff in the LEO section on doing something like this.

As I was reading what you were wanting to do with this I began to wonder if one of those jumper battery packs might work for something like this. I know you are in the UK but they must have something like that over there. Potentially you could get a couple of things in one device. I have seen some that include air compressors, lights and USB power sources for charging things like cell phones. That could be real handy if you did any camping. Besides they are going to be sealed well and you would have little risk of them shorting out on something in the bike when not hooked up. I think you were considering wiring this to the bike but by having it separate and just making sure you have a spare key you are simplifying things and should it ever go bad they are easily replaced. Also they are completely sealed so you don't have to worry about a lead acid battery leaking on you.

Something like this.

http://www.amazon.com/Black-Decker-VEC026BD-Electromate-Jump-Starter/dp/B000EJS9IM/ref=sr_1_2?ie=UTF8&qid=1339616925&sr=8-2&keywords=battery+pack+jump+start

or this

http://www.amazon.com/Stanley-J5C09-500-Amp-Built-In-Compressor/dp/B002X6VXL4/ref=sr_1_4?s=automotive&ie=UTF8&qid=1339617150&sr=1-4&keywords=jump+starter

 

[Andi As]

Have you considered fitting an isolator switch to the battery lead say under the seat, so that you can flick it off when its sat for a few weeks.Alternatly do you have power were you store the bike as you could just connect it to a slow charge tender in the garage when not in use?

 

[T_C]

It does beg the question.. why is your battery dying so much? Got a 60 watt light bulb flashing on the alarm circuit? If your bike is stock and just sitting for a week between rides it should not be draining the battery down that far. Now if it is sitting for weeks or months between rides, then yep, put a slow charger on it to maintain it. Battery Tender is the popular brand, but plenty of others on the market. I have a pair of Schumachers that work good. Heck the little float charger Harbor Freight sells for $5 on special works good.. if you have a Harbor Freight there.

 

[Fearmor]

Why not connect your bike to a Trickle Charger when you,re not useing it.It will keep the battery topped up and won,t be taking up space when you,re rideing.They are also cheaper than a battery,I bought mine(Oxford) on ebay for less than 50 euro

 

[NorCalBusa]

If you go LiFe; be certain you don't draw it below 13v or you can ruin the battery (and it won't be warranty- they can tell). Also be sure your charger has the de-sulfate mode inhibited if its connected to LiFe.

 

[T_C]

If you go LiFe; be certain you don't draw it below 13v or you can ruin the battery

Norcal, is this in the manual? Have a link? I'm curious.. nominal voltage on a LiFe battery is 3.2 per cell. So on standard battery that is 12.8v. Most of the high amperage cells I have seen list a minimal discharged voltage of between 2.0v~2.5v. Did someone come up with a new design and chemistry? You got me wondering...

 

[st1300r]

resting voltage below 12.86 aka c. 20% remaining charge is verboten. That's for LiFePO4.

 

[T_C]

resting voltage below 12.86 aka c. 20% remaining charge is verboten. That's for LiFePO4.

Okay.. doing the math... they are claiming full voltage is 3.585, which is right in line, most claim 3.6~3.65. Full discharge is 2.3v, again in line with most cells being 2.0~2.5. So looks like these are standard high current LiFe cells.

I think the word translation is where I am getting lost. Resting voltage.. as in storage, long term storage. Not useable voltage, storage voltage.

No, you should not store a Li battery (any type) at a fully discharged state. 75% or so of charge is the recommended level for storage. It is fine to take this battery down to 9.2v, just don't leave it there. Every Li battery should have a battery management circuit in it that cut's off each cell in the battery once it falls to the minimum voltage. (If you go below there.. you risk fire, :cf1:, breakout the marshmallows, also.. don't puncture a battery... damhikt) Taking a Li battery down to the lowest recommended voltage does not hurt it... as long as you don't leave it there for a long time. Promptly get the battery charged back up.

 

[st1300r]

Resting=not under load.
(the environment in which you can use voltage to estimate % charge)

IOW freshly charged then a brief load (for lead acid anyway) to remove surface charge.
At that point it can be used to estimate the state of charge.
After cranking it will show a depressed voltage that eventually recovers.

Lithium ion batteries using iron have a lower capacity loss over time than other lithium ion batteries and tend to be more stable than other lithium ion chemistries although they do share simililar characteristics.

 

[T_C]

Resting=not under load.
(the environment in which you can use voltage to estimate % charge)

Yep, that is another way of stating it. But I don't see that as applying to this chart. Or maybe I should say the person making this chart does not understand LiFe characteristics.

I was just confused with the original statement that you shouldn't draw a LiFe under 13v. You can take it under that, just don't leave it there for extended periods.

 

[NorCalBusa]

Great advice TC, and true for virtually all batteries. They are happiest (and last longest) when in a charged state. Use them, but be sure to charge back up right away.